The present invention is directed to a device for analog-to-digital conversion and, more particularly, a plurality of analog-to-digital converters that are capable of being synchronized with each other.
As the very name already indicates, AND converters (analog-to-digital converters) convert analog signals into digital signals. Innumerable embodiments have been known for many years and require no further explanation.
It is definitely necessary to know voltage levels of a plurality of analog signals acquired exactly simultaneously (absolutely time-synchronized). This is required, for example, to set (regulate) the phase currents of electric motors exactly as desired or in order to implement position acquisitions ensuing according to the resolver principle.
When only one A/D converter is available for the time-synchronous acquisition of a plurality of analog signals, then the time-synchronous acquisition of the plurality of analog signals can be accomplished by providing a plurality of sample and hold elements (SandH elements). The analog signals to be acquired time-synchronously can be simultaneously sampled by the plurality of SandH elements and can be serially A/D-converted by the one A/D converter. Providing, driving and coordinating, the A/D converter and the plurality of SandH elements, however, can involve a considerable cost outlay.
A conceivable alternative to the above alternative is to provide a plurality of A/D converters. As a result thereof, the analog signals to be acquired can not only be time-synchronously sampled but can also be time-synchronously converted. When, in particular, the unit controlling the A/D converters is a program-controlled unit such as, for example, a microprocessor or a micro-controller, it proves extremely difficult, however, to start the plurality of A/D converters exactly simultaneously. In general, a plurality of clock periods of the program-controlled unit lie between the delivery of an A/D conversion request to a first A/D converter and the delivery of an A/D conversion request to a second A/D converter. When the program-controlled unit must react to an interrupt (implement an interrupt service routine) between the delivery of the A/D conversion requests to the various A/D converters, the time difference between the delivery of the A/D conversion requests to the various A/D converters becomes even greater. This, even an approximately simultaneous start of the plurality of A/D converters cannot be assured.
The present invention is therefore based on an object of finding a solution to dependably start a plurality of A/D converters exactly simultaneously with minimal outlay.
This and other objects are inventively achieved by an A/D converter that is designed to signal the beginning or the impending beginning of an A/D conversion; an A/D converter that is designed to request the implementation of an A/D conversion from another A/D converter.
As a result that it is possible for a plurality of A/D converters to cooperate with one another. In particular, the request for the implementation of an A/D conversion by another A/D converter or signaling the beginning or the impending beginning of an A/D conversion makes it possible for the plurality of A/D converters to independently synchronize with one another (i.e., without the collaboration of a higher-ranking control means) such that they work exactly time-synchronously when required.
Additional advantages and novel features of the invention will be set forth, in part, in the description that follows and, in part, will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.